BREATHING
=The Lungs.=--The lungs are two light spongy bodies filling up the
greater part of the chest. The heart lies between the lungs. The
lungs are formed largely of thousands of thin-walled sacs and two sets
of tubes. One set of tubes carries air into and out of the lungs, and
the other set is filled with blood. These sacs and tubes are held in
place by a loose meshwork of tissue.
[Illustration: FIG. 54.--The ribs and front wall of the chest cut away
to show the lungs. A piece of one lung is cut off to show the heart.
_A_ and _E_, parts of the breastbone; _F_, diaphragm.]
=Why we Breathe.=--Breathing means taking air into the lungs and
forcing it out. The air is made to go into the lungs in order that a
part of it called oxygen may get into the blood. The blood then
carries the oxygen to all parts of the body where it can help the
organs do their work.
[Illustration: FIG. 55.--Photograph of a salamander, showing the gills
on either side of the head, which are used in breathing.]
The air which comes out of the lungs is not the same as that which
goes in. Some of the oxygen has been used up and in its place is a
heavier gas named _carbon dioxide_, which has been given out by the
body. This carbon dioxide is part of the waste formed in every part of
the body from the used-up food and dying parts of the body. We breathe
therefore to get oxygen into the body and to take out some of the
waste matter.
All animals must breathe. If our breath is shut off only four or five
minutes, death results. In the earthworm the oxygen goes right through
the skin into the blood. Bugs and flies have several little openings
along the sides of the body which lead into tubes branching throughout
the body to carry air. A fish gets air through its gills lying under a
bony flap on each side of the head.
[Illustration: FIG. 56.--The windpipe and lungs viewed from in front.
On the right, the tissue is removed to show the air tubes.]
=How the Air passes into the Lungs.=--The outer openings of the nose
are called nostrils. From here two channels lead back through the nose
to the throat. The cavity of the throat behind the nose and tongue is
the _pharynx_. At the bottom of the pharynx is a tube made mostly of
gristle. This tube is larger than your thumb and is named the
_larynx_, or _voice box_. The bump on its front part forms the lump in
the throat called the _Adam's Apple_.
From the voice box extends the _windpipe_ called _trachea_, down to
the lungs. The windpipe divides at its lower end between the lungs
into two branches. One of these enters each lung.
=The Air Tubes in the Lungs.=--As the branch of the windpipe enters
each lung it divides into smaller branches just like the limbs of a
tree. These divide into still smaller tubes, which branch again and
again until they are as small as a hair. These hairlike tubes have
swollen ends called _air sacs_. The walls of the air sacs are much
thinner than tissue paper.
[Illustration: FIG. 57.--A bunch of air cells at the end of an air
tube in the lungs, showing the blood vessels which receive the oxygen
and give out the carbon dioxide.]
=How the Blood trades Waste for Oxygen in the Lungs.=--The blood,
which is constantly running from all parts of the body to the lungs,
collects waste formed from the burnt food and dying parts of the
organs. When the blood comes to the lungs, it is full of this waste,
called carbon dioxide. The blood tubes divide into fine branches with
very thin walls and form a rich network over the air sacs. This allows
the carbon dioxide and water to pass out of the blood tubes into the
air sacs, while the oxygen at the same time goes through into the
blood. More than a pint of water is given off in the breath daily.
=How we Breathe.=--The bottom of the chest cavity is formed by an
upward arching sheet of muscle called the _diaphragm_. This is
fastened to the lower ribs. The ribs at rest slant downward and
inward. When the ribs are pulled up or the arch of the diaphragm down,
the cavity of the chest becomes larger. The air then runs into the
lungs and swells them out. When the ribs are let drop or the arch of
the diaphragm goes up, the air is pushed out of the lungs.
Without thinking, we work the muscles to draw up the ribs about
eighteen times every minute, because all parts of the body are calling
for oxygen. The harder we work the oftener we breathe because the
muscles need more oxygen to make them go.
=Why we should breathe through the Nose.=--Most persons find it easy
to breathe through the nose. In some, however, the passages in the
nose are too small to carry the air without effort. On this account
they let the mouth hang open and breathe through it.
[Illustration: FIG. 58.--Face cut through the middle to show how the
adenoids stop the air from passing through the nose. Arrows show the
course which the air should take.]
The air should pass only through the nose because it is lined with
hairs and tiny waving threads which catch the dust. In this way germs
and dirt are prevented from getting into the throat and lungs, and in
winter the cold air is warmed.
=Why Some Children cannot breathe through the Nose.=--When one has a
cold, the lining of the nose becomes swollen and gives out a white
substance called _mucus_. The swelling of the lining and the mucus fill
up the passages. The nose should be kept clean by using a handkerchief
and blowing out the mucus into it. _Never put the finger into the nose._
Disease germs often get on the fingers from things touched.
Children who have the habit of breathing through the mouth should be
examined by a physician. He will, in most cases, find soft spongy
growths called _adenoids_ in the back part of the nose. They should
always be removed as soon as possible. They may cause disease or
deafness and may even injure the mind.
[Illustration: FIG. 59.--A view of the voice box from the top.]
=The Voice.=--In the upper part of the voice box at the top of the
windpipe is a fold of tissue stretched on either side. These two folds
of tissue form the _vocal cords_. The air rushing past them causes
sound. The different sounds are made by stretching the cords tight or
loosely. By means of the tongue, teeth, and lips the sound is formed
into words.
=How to use the Voice.=--A cold or much shouting makes the vocal cords
swell and we become hoarse. Rest is the best cure. It is not polite to
shout or whistle in the house and you should never use an angry tone
of voice. When talking to a person, always speak distinctly but
pleasantly and turn your face toward his and look directly into his
eyes. Never use a harsh, loud tone of voice.
=Why you should not spit on Floors or Sidewalks.=--We used to think
that any one well had no germs of sickness in his mouth, but we now
know that many well persons have germs in their mouths which can cause
long sickness when they get into other persons. If you are sick with
diphtheria, scarlet fever, or sore throat, the germs of the disease
are likely to remain in your mouth two or three months. Persons with
tuberculosis throw out millions of these germs in their spit every day.
Spitting is not only an unclean habit but a deadly curse. Spit often
contains the seeds of death. Women's skirts and the soles of our shoes
carry it into the houses. It becomes dry, but the germs live and float
about in the dust, then enter the mouth to make us sick. Carelessness
with spit is said to cause more than a hundred deaths every day in our
land.
=Do not use an Open Spittoon.=--It is much safer to have a smallpox
patient in the house than an open spittoon in the summer. You can
prevent the smallpox by vaccination, but you cannot keep the flies
from carrying ten thousand germs of death from the spittoon to the
food on the table. A million germs have been found on a single fly.
[Illustration: FIG. 60.--Photograph of a house fly on a piece of bread.
This fly had been feeding on spit and a study of its legs and body
showed more germs present than there are hairs on a person's head.]
Spit should be dropped into a cup which should be kept covered when
not being used. The spit should be destroyed by fire or some
germ-killing fluid, such as lye or formalin.
[Illustration: FIG. 61.--An exact drawing of the germs in a spot as
large as a period, on the edge of a drinking cup.]
=Keeping Sickness away from the Throat and Lungs.=--All sickness of
the throat and lungs is caught from some one else. The germs are
passed from one to another on the drinking cup, by sucking pencils,
wetting the finger to turn the pages of a book, or putting the fingers
in the nose or mouth.
[Illustration: FIG. 62.--A dish of beef broth jelly left open two
minutes in a room being swept. Each spot is a city of thousands of
germs which grew from one germ dropping on the jelly. By counting the
spots you can tell how many germs fell from the dust on this dish
three inches in diameter.]
_Dust is the partner of disease._ It contains germs. Avoid dust. Wipe
up the rooms with a damp cloth; never use a feather duster. Avoid dry
sweeping. Use a suction cleaner or have rugs which can be cleaned out
of doors.
Give the lungs fresh air and deep breathing and the body good food and
plenty of sleep to make it so strong that germs cannot overcome it
when they enter.
[Illustration: FIG. 63.--Photograph of consumption germs, the tiny
rods which often grow and cause tuberculosis in bodies weakened by
beer or whisky. Much enlarged.]
=Alcoholic Drink and the Lungs.=--The most common disease of the lungs
is _tuberculosis_. Nearly all bartenders who sell strong drink take
some themselves. Lately it has been learned in Germany that
tuberculosis causes one half of all the deaths among bartenders.
Alcohol was once thought to be a good medicine for lung troubles, but
it has been clearly proven that beer and whisky weaken the lungs and
make them ready for the germs of disease. The body already weakened by
the poison of the alcohol is then easily overcome by the disease.
=Tobacco and the Lungs.=--The occasional use of tobacco does not seem
to hurt the lungs when fully grown. A study of many young persons has
shown that the chest of smokers grows much more slowly than in those
who do not use tobacco. As the lungs cannot grow any faster than the
chest, they must grow slowly in boys using much tobacco.
Tobacco is a common cause of sore throat. Many smokers have been
compelled to quit the habit because of throat troubles.
PRACTICAL QUESTIONS
1. Where are the lungs located?
2. What do the tubes in the lungs carry?
3. What part of the air do we use in the body?
4. Tell how the air gets into the lungs.
5. What passes from the blood into the air sacs?
6. Why should we breathe through the nose?
7. Why should you keep the fingers away from the nose?
8. What are the vocal cords?
9. Give two reasons why no one should spit on the floor.
10. Tell how alcohol harms the lungs.